an a Tuesday night. We're learning more about robin Williams and what played out in his home. Police reveal what they believe happened inside his home in California. His body found by his personal assistant. Tonight the tributes pouring in from around the world, this home in Boulder, Colorado, the background drop for "Mork and Mindy." A similar picture where he filmed "Mrs. Doubtfire." Robin Williams had just signed on to reprise that roll. The Hollywood walk of fame surrounded by candles and messages from grieving fans. ABC's Cecilia Vega leads us off from the back drop in San Francisco and we know that robin Williams called the bay area his home. Reporter: David, good evening. You can see there's a crowd that has poured into this sidewalk. These famous stairs at that house that you mentioned overwhelmed with flowers and candles, all of this to remember a man who will be missed by so many. Reporter: Tonight, new details about robin Williams' final hours. At 10:30 P.M. Sunday night, Williams was last seen alive by his wife, Susan Schneider. Investigators say she woke up Monday morning and left their house, thinking her husband was still asleep. But just before noon, his personal assistant discovered his body. Distraught, she called 911. Emergency crews responded in minutes. Apparent suicide by hanging. Our indication is that it is a suicide due to asphyxia due to hanging. Reporter: A pocket knife found near his body, cuts on his wrist. Mr. Williams had been seeking treatment for depression. Reporter: This long time friend who saw Williams just last week told me he and others close to him were concerned. We've been worried. He's been fragile. He's been like really -- it was clear to us that, you know, that he was not in great shape. Did you think it would come to this? No. I mean, no. I mean, he was getting so much love and support all around him. You know, it's -- for me there's no making sense of any of this. Reporter: Today those landmarks made famous over the course of a legendary career now memorials, from that bench in Boston seen in "Good will hunting" -- You don't know about real loss. That only occurs when you love something more than you love yourself. Reporter: Now surrounded by tributes written in chalk to his star on the Hollywood walk of fame, spilling over with flowers and notes as fans mourn the loss of a movie legend, Williams' family mourned in private, his wife saying in a statement, I am utterly heartbroken and his daughter Zelda tweeting this message, I love you, I'll miss you, I'll try to keep looking up. From those who worked with Williams, the tributes pour in. Steven Spielberg, robin was a lightning storm of comedic genius. Whoopi Goldberg expressing the sadness of so many, Billy crystal is right, there are no words. Ben Affleck saying tonight, he made Matt and my dreams come true. What do you owe a guy who does that? Everything. Reporter: Gary marshal discovered Williams, saying he had more energy than anyone in any room. Marshall today saying the first time he met robin Williams, Williams stood on his head in an office chair. David, always the comedian. Hired on the spot. He said he had never interviewed an alien before. That's how he got the job for "Mork and Mindy." Tough question to ask but was there any note, any message left for his family? Do we know yet? Reporter: We don't know, David. Investigators aren't saying whether he left behind a suicide note but they are saying that this investigation will remain open as they await the results of a toxicology test.

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